We request funds for the purchase of an FEI Quanta 200 field emission scanning electron microscope (FESEM) together with a Gatan Model 681 ion beam sputter coater. The microscope and sputter coater will provide for the scanning electron microscopy needs of nine major and three minor users at the University of Massachusetts Medical School. The microscope will be housed in the Core Electron Microscopy Facility of the Medical School, and will replace the only other instrument available - an obsolete 30-year old SEM that is out of service much of the time, lacks key capabilities, and is proving impossible to repair due to its age and the unavailability of spare parts. The ion beam sputter coater will replace a conventional 15-year old sputter coater and is required to provide the fine grain coatings needed for high resolution studies. The projects that will use SEM include studies of the functioning of cell surface receptors involved in immune recognition, the development and function of cilia, the structure of normal and diseased bone, structural changes in mutants of signaling and other proteins in mice and Drosophila, and cell surface structures involved in bacterial infection. These projects require FESEM for two main purposes - the imaging of cell surface structure at high resolution, and the detection and localization of specific cell surface antigens by immuno-FESEM. These images will provide essential insights into the mechanisms of cell development, function, infection, and disease. In addition to the users on this grant, there are approximately twenty other investigators at the medical school who would use SEM if we had a functioning instrument. A state-of-the-art SEM, with field emission gun, has become essential to meet this need. It will transform the ability of investigators to carry out their SEM-related studies, it will greatly improve the quality and speed of data collection, and it will make possible observations that are impossible on our current instrument. All of the projects that will use this microscope aim to provide fundamental insights into cellular structure and function. Many have a direct bearing on the understanding of human disease. Results provided by this instrument will play a key role in advancing our knowledge in these areas. [unreadable] [unreadable] [unreadable]